This invention pertains to a slidegate assembly and method for use with foundry ladles, steel mill ladles, and the like for regulating the flow of molten melt.
Slidegate assemblies, which are one of the more commonly used methods for metering the flow of molten melt, generally comprise a stationary plate having an opening therein and secured to the ladle to align the opening with the outlet in the ladle. A second slidegate is slidably mounted against the stationary slidegate and is slidable between an open position wherein an opening in the second slidegate is aligned with the opening in the stationary slidegate, and a closed position wherein the second slidegate is moved to close the opening in the stationary slidegate. Due to corrosive and, particularly, erosive effects, high temperatures, and the like of the molten melt, the slidegates are generally made of a heat-resistant material, such as fireclay. Though made of a heat-resistant material, the slidegates are generally useable for only one pouring operation and then must be replaced because of erosion or cracking caused by the molten melt. Erosion of the slidegates, particularly about their openings, precludes a satisfactory fluid-tight seal between the slidegates, and any cracks will eventually travel to the peripheries of the slidegates and cause leaking of the melt.
Various attempts to provide slidegates resistant to the effects of molten melts include manufacturing each of the slidegates of an extremely hard refractory material more resistant to the erosive effects of molten melt than fireclay. However, one of the drawbacks with these slidegates is that the refractory material of which they are made is extremely expensive, and for that reason are undesirable.
Another method attempted to improve the resistance of slidegates to the effects of the molten melt includes coating slidegates made of fireclay or the like with an extremely hard refractory material, such as zirconium silicate, corundum, or the like. One of the problems with this is that the means for adhering or bonding the coating to the slidegate is generally not sufficient to withstand the extremely high temperatures and erosive effects of the molten melt during multiple pouring operations. These coatings tend to chip or break off due to the failure of the adhesive or bonding technique utilized. Further, once a crack develops in the coating, it will eventually travel to the edge of the coating, thereby causing leaking of molten melt.
Moreover, should only portions of the sliding surfaces near their openings be coated with the hard refractory material, the loss of flatness or planarity of the sliding surfaces due to the partial coating can cause leakage during sliding movement between the open and closed positions.